• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.435-435
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• 2010

A inclined slot-excited plasma source is newly designed and constructed for higher flux HNB(Hyperthermal Neutral Beam) generation. The present source is different from the vertical SLAN(SLot ANtenna) sources [1] in two aspects. One is that the slots are inclined, and the other is that the magnetic field is configured to a cusp type. These modifications are intended to make the source plasma operated in sub-milli-torr pressure regime and as thin as possible, both of which is to get higher HNB flux by decreasing the re-ionization rate of the reflected atoms from the neutralizer [2]. The plasma is generated in a quartz tube of internal diameter 170 mm enclosed in a aluminum application chamber of larger diameter 250 mm. The microwave power is fed to the plasma chamber by 8 inclined slots cut into the application chamber wall. The slots are coupled the chamber to a WR280 waveguide wound around it to form a ring resonator. In order to make two slots $\lambda_g/2$ apart in phase, the adjacent slots are rotated in opposite directions. The rotation angle of the slots are set to $60^{\circ}$ from the chamber axis. Between the quartz chamber and the aluminum cylindrical chamber 8 NdFeB magnets are equally spaced and fixed to form the cusp magnetic field confinement and ECR (Electron Cyclotron Resonance) field. In this presentation, the magnetic and electromagnetic simulations, and the measured plasma parameters are given for both the inclined and the vertical slot-excited plasma sources. We also discuss how the sources can be tailored to suit better-performing HNB sources.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.3
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• pp.186-195
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• 2010

This study has attempted to suggest a proper reinforcement method by strengthening unbonded post -tensioning through height of an anchorage hole, form of a saddle, and loading time point as parameters and evaluating the reinforcement method through a bending experiment. The result of this experiment indicated effects of reinforcement since the maximum strength ratio(the ratio of an experimental value to theoretical value) of SC composite beams before prestressed was 0.97 and after prestress were 1.00~1.21. As a result of analysis on displacement and strain, irrespective of height of an anchorage hole and loading time point, the D120-series specimen where an anchorage hole was installed on the neutral axis after reinforcement showed that its deflection continuously increased without sudden load reduction after maximum load and it stably behaved with relatively low strain of each part. In terms of reinforcement effects, the maximum strength of SCR-UD120 specimen prestressed after pre-loading was increased 1.72 times comparing to SC composite beams so SCR-UD120 specimen prestressed after pre-loading was shown to be the best.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.1 s.145
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• pp.15-21
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• 2006

Recently, the attention to large container ships whose size is greater than 10,000 TEU container ship has been increased due to their increasing demand. The large container ship has twin skegs because of the engine capacity and large beam-draft ratio. In this paper, the maneuvering characteristics of a container ship with twin skegs were investigated through 4DOF(four degree of freedom) HPMM(Horizontal Planar Motion Mechanism) test and computer simulation. A mathematical model for maneuvering motion with 4DOF of twin skegs system was established to include effects of roll motion on the maneuvering motion. And to obtain roll-coupling hydrodynamic coefficients of a container ship, 4DOF HPMM system of MOERI which has a roll moment measurement system was used. HPMM tests were carried out for a 12,000 TEU class container ship with twin skegs at scantling load condition. Using the hydrodynamic coefficients obtained, simulations were made to predict the maneuvering motion. Rudder forces of twin-rudders were measured at the angles of drift and rudder. The neutral rudder angles with drift angles of ship was quite different with those of single skeg ship. So other treatment of flow straightening coefficient $\gamma_R$ was used and the simulation results was compared with general simulation result. The treatment of experimental result at static drift and rudder test was very important to predict the maneuverability of a container ship with twin skegs.

• Nuclear Engineering and Technology
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• v.54 no.11
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• pp.4134-4145
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• 2022

The collimator is one of the high-heat-flux components used to avoid a series of vacuum and thermal problems. In this paper, the heat load distribution throughout the collimator is first calculated through experimental data, and a transient thermodynamic simulation analysis of the original model is carried out. The error of the pipe outlet temperature between the simulated and experimental values is 1.632%, indicating that the simulation result is reliable. Second, the model is optimized to improve the heat transfer performance of the collimator, including the contact mode between the pipe and the flange, the pipe material and the addition of a twisted tape in the pipe. It is concluded that the convective heat transfer coefficient of the optimized model is increased by 15.381% and the maximum wall temperature is reduced by 16.415%; thus, the heat transfer capacity of the optimized model is effectively improved. Third, to adapt the long-pulse steady-state operation of the experimental advanced superconducting Tokamak (EAST) in the future, steady-state simulations of the original and optimized collimators are carried out. The results show that the maximum temperature of the optimized model is reduced by 37.864% compared with that of the original model. The optimized model was changed as little as possible to obtain a better heat exchange structure on the premise of ensuring the consumption of the same mass flow rate of water so that the collimator can adapt to operational environments with higher heat fluxes and long pulses in the future. These research methods also provide a reference for the future design of components under high-energy and long-pulse operational conditions.

• Journal of the Korean Institute of Landscape Architecture
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• v.41 no.1
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• pp.21-33
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• 2013

The purpose of this study is to find applicabilities of human bioclimatic maps, using human thermal sensation(comfort) in summer, with microclimatic in situ data and computer simulation results at the study site of downtown Daegu. This includes the central business district(CBD) area and two urban parks, the Debt Redemption Movement Memorial Park and the 2.28 Park, for urban and landscape planning and design. Climatic data and urban setting information for the analysis of human thermal sensation were obtained from in situ measurement and the geographic information system data. As a result, the CBD had higher air temperature than the parks when the wind speed was low. Relative humidities were opposite to the air temperature. Especially, same directional streets with local wind direction had lower air temperature than streets perpendicular to the wind direction. The most important climatic variable of human thermal sensation in summer was direct beam solar radiation. Also, creating shadow areas would be the most relevant method for modifying hot thermal environments in urban areas. The most effective method of creating shadow patterns was making a tree shadow over a pergola, and the second best one was making a tree shadow on the front of north directional building walls. Moreover, how to plant trees for creating shadow patterns was important as well as what kind of trees should be planted. The results of human thermal sensation were warm to very hot at sunny areas and neutral to warm at shaded ones. At the sunny areas, wide, squared shape areas had a little bit higher thermal sensation than those of narrow streets. The albedo change of building walls 0.15 and ground surface 0.1 could change 1/6 of a sensation level at the shaded areas and 1/3 at the sunny ones. These microclimatic approaches will be useful to find appropriate methods for modifying thermal environments in urban areas.

• Journal of Technology Innovation
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• v.22 no.4
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• pp.145-164
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• 2014

Nuclear fusion is one of the most promising options for generating large amounts of carbon-free energy in the future. Major countries such as China, EU, and Japan have established a national plan for DEMO construction and they are implementing it. Korea has started a nuclear fusion research and development by the KSTAR project started in 1995. There are matured needs for a full-scale research and development initiatives to ensure competition with the major countries for DEMO as well as achieve the final goal to commercialize fusion energy. In this paper, we apply the TRL and AHP methods in order to identify the key technologies to conduct DEMO R&D. We propose the priorities of future R&D on DEMO by deriving a core technology in the field. At first, we review the scientific theory of fusion and trend of progress of DEMO activities in major countries. For previous studies, we review TRL and AHP methods to examine the technology classification system of DEMO and identify key technologies. We apply TRL method to identify readiness level of DEMO technologies and AHP to compensate shortcoming of TRL. The key technologies of DEMO to be secured from a synthesis result of the TRL and AHP are burning plasma, plasma facing material, structural material, high frequency heating, neutral particle beam, safety, plasma diagnostic, and simulation technologies.

• Journal of Korean Society of Steel Construction
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• v.28 no.2
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• pp.109-120
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• 2016

Flexural tests of full-scale concrete-filled U-shape hybrid composite beams were conducted. Ordinary (SS400) and high-strength (SM570) steel plates were used in the web and in the bottom flange of U-shape steel section respectively. The primary objectives were to develop the hybrid section configuration with maximized flexural capacity and to investigate its flexural strength and deformation capacity. All the hybrid test specimens in this study exhibited the plastic moment capacity and resonable deformability. It is shown that the plastic stress distribution can be assumed in calculating the flexural strength of the proposed hybrid composite beams if the plastic neural axis is located within 15% of the total beam depth from the top of the composite slab. The procedure for computing the effective flexural stiffness of hybrid composite beams is also recommended based on test results.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.100-101
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• 2012

The plasma damage free and room temperature processedthin film deposition technology is essential for realization of various next generation organic microelectronic devices such as flexible AMOLED display, flexible OLED lighting, and organic photovoltaic cells because characteristics of fragile organic materials in the plasma process and low glass transition temperatures (Tg) of polymer substrate. In case of directly deposition of metal oxide thin films (including transparent conductive oxide (TCO) and amorphous oxide semiconductor (AOS)) on the organic layers, plasma damages against to the organic materials is fatal. This damage is believed to be originated mainly from high energy energetic particles during the sputtering process such as negative oxygen ions, reflected neutrals by reflection of plasma background gas at the target surface, sputtered atoms, bulk plasma ions, and secondary electrons. To solve this problem, we developed the NBAS (Neutral Beam Assisted Sputtering) process as a plasma damage free and room temperature processed sputtering technology. As a result, electro-optical properties of NBAS processed ITO thin film showed resistivity of $4.0{\times}10^{-4}{\Omega}{\cdot}m$ and high transmittance (>90% at 550 nm) with nano- crystalline structure at room temperature process. Furthermore, in the experiment result of directly deposition of TCO top anode on the inverted structure OLED cell, it is verified that NBAS TCO deposition process does not damages to the underlying organic layers. In case of deposition of transparent conductive oxide (TCO) thin film on the plastic polymer substrate, the room temperature processed sputtering coating of high quality TCO thin film is required. During the sputtering process with higher density plasma, the energetic particles contribute self supplying of activation & crystallization energy without any additional heating and post-annealing and forminga high quality TCO thin film. However, negative oxygen ions which generated from sputteringtarget surface by electron attachment are accelerated to high energy by induced cathode self-bias. Thus the high energy negative oxygen ions can lead to critical physical bombardment damages to forming oxide thin film and this effect does not recover in room temperature process without post thermal annealing. To salve the inherent limitation of plasma sputtering, we have been developed the Magnetic Field Shielded Sputtering (MFSS) process as the high quality oxide thin film deposition process at room temperature. The MFSS process is effectively eliminate or suppress the negative oxygen ions bombardment damage by the plasma limiter which composed permanent magnet array. As a result, electro-optical properties of MFSS processed ITO thin film (resistivity $3.9{\times}10^{-4}{\Omega}{\cdot}cm$, transmittance 95% at 550 nm) have approachedthose of a high temperature DC magnetron sputtering (DMS) ITO thin film were. Also, AOS (a-IGZO) TFTs fabricated by MFSS process without higher temperature post annealing showed very comparable electrical performance with those by DMS process with $400^{\circ}C$ post annealing. They are important to note that the bombardment of a negative oxygen ion which is accelerated by dc self-bias during rf sputtering could degrade the electrical performance of ITO electrodes and a-IGZO TFTs. Finally, we found that reduction of damage from the high energy negative oxygen ions bombardment drives improvement of crystalline structure in the ITO thin film and suppression of the sub-gab states in a-IGZO semiconductor thin film. For realization of organic flexible electronic devices based on plastic substrates, gas barrier coatings are required to prevent the permeation of water and oxygen because organic materials are highly susceptible to water and oxygen. In particular, high efficiency flexible AMOLEDs needs an extremely low water vapor transition rate (WVTR) of $1{\times}10^{-6}gm^{-2}day^{-1}$. The key factor in high quality inorganic gas barrier formation for achieving the very low WVTR required (under ${\sim}10^{-6}gm^{-2}day^{-1}$) is the suppression of nano-sized defect sites and gas diffusion pathways among the grain boundaries. For formation of high quality single inorganic gas barrier layer, we developed high density nano-structured Al2O3 single gas barrier layer usinga NBAS process. The NBAS process can continuously change crystalline structures from an amorphous phase to a nano- crystalline phase with various grain sizes in a single inorganic thin film. As a result, the water vapor transmission rates (WVTR) of the NBAS processed $Al_2O_3$ gas barrier film have improved order of magnitude compared with that of conventional $Al_2O_3$ layers made by the RF magnetron sputteringprocess under the same sputtering conditions; the WVTR of the NBAS processed $Al_2O_3$ gas barrier film was about $5{\times}10^{-6}g/m^2/day$ by just single layer.